Precise measurements from each control point
are stored in the NSCRS database. These points represent exact
locations on the irregularly shaped Earth.

The Earth's irregular shape is replaced by a
geometric shape (ellipsoid) upon which computations are made at
various points.

A cylinder is placed around the Earth and
the computed points are transfered from the globe onto the
cylinder's surface.

The cylinder is unrolled, producing a two dimensional map.

There is no way to accurately portray a round, threedimensional
object on a flat, twodimensional piece of paper. Since the Earth is not
perfectly round and flat, any attempt to represent the Earth on paper will
distort shape, distance, or direction. Older world map projections, for
instance, would shrink Africa (near the equator) and expand Canada (near
the pole), creating an unrealistic difference in apparent size. Although
such inaccuracies are not normally noticeable on a map of Nova Scotia specifically,
it is important to understand they exist and they are taken into consideration
when maps are produced.
A datum is a threedimensional
coordinate system which has a defined point of origin and orientation and
a specific mathematical figure (ellipsoid) defined. Simply put, it is used
to calculate where the real world coordinate points should be in relation
to each other on the twodimensional map. As new methods of measuring and
gathering information have improved, new datums have evolved to meet these
changing needs.
The NSCCS uses the Average
Terrestrial System of 1977 (ATS77), while the new NSHPN uses the North
American Datum NAD83 (CSRS).
The province has used the 3º
Modified Transverse Mercator as its standard with the ATS77 (and earlier)
datum. With the new NAD83 datum, the province will move to the 6º UTM
projection, bringing Nova Scotia in line with other jurisdictions,
including the federal government.
